1. Field of the Invention
The present invention is generally directed to an electronic navigation device employing a receiver for receiving GPS satellite signals. More particularly, the present invention is directed to an electronic navigation device and method for displaying a navigation route in a perspective view on a display screen of the device.
2. Description of the Related Art
Electronic navigation devices employing GPS receivers have become increasingly popular in recent years. The devices utilize an electronic satellite navigation system which permits a user of the system to determine his or her position with respect to the earth. Such navigation devices are extremely useful in navigation vehicles of all types, including aircraft, marine craft, and land vehicles. Additionally, the devices are useful for tracking purposes, and hand held versions are popular with hikers and campers.
Very generally, conventional electronic navigation devices employ a receiver which detects signals from a number of satellites orbiting the earth. A processor within the navigation device computes the location of the device, based upon data received from the received satellite signals, after a sufficient number of GPS satellite signals have been acquired. Particularly, once a sufficient number of GPS satellite signals are acquired, the device is able to calculate its position with respect to the various satellites. Thus, an electronic navigation device employing a GPS receiver has the ability to accurately compute the position of the device on or near the earth in real time, even as the device moves, in addition to being able to calculate the velocity and direction at which the device is moving in three dimensions.
U.S. Pat. No. 5,323,164 to Endo teaches a satellite radio wave capturing method for a global positioning system receiver. U.S. Pat. No. 5,225,842 to Brown, et al. teaches a vehicle tracking system employing global positioning system satellites. Each of these patents is incorporated herein by reference.
Both recreational and professional users of navigation equipment seek intuitive representations of navigation information which are direct and simple to interpret. The ability of a navigation device to present navigation information in a manner that is simple to interpret is particularly important to professional users, who use the equipment as one basis for navigating a vessel, such as an aircraft or marine craft.
Many conventional navigation devices use what is commonly referred to as a "highway" representation, where an intended navigational course or route is presented on a display screen as a line drawn to a horizon, with borders creating a lane which all converge at a vanishing point on the horizon. By orienting this image of the intended path of navigation with the user's or vessel's orientation, an intuitive steering guide results for keeping a navigator on course. While the interpretation of such a navigational aid is indeed intuitive and helpful, it falls short of achieving the ultimate goal of displaying all navigation information in a true perspective, or in a virtual presentation, where spacial relationships between the navigator and various points of interest, such as turn events or hazards, are correct, even for navigational routes which consist of multiple legs at varying angles to each other.
Another prior art method of displaying navigational information draws a single lane, indicative of an active route leg, on the display screen. The leg doesn't truly converge to any vanishing point. Rather, the lane rotates, depending upon the navigator's relationship to the intended path of navigation indicated by the lane. A primary drawback of this prior art approach is that, when the navigator gets off course, for instance when the navigator is oriented sidewise relative to the course, the device is unable to display anything meaningful. This problematic prior art approach is illustrated in FIGS. 2b and 2c, and described in greater detail below.
An additional prior art approach is to show multiple legs of a route from a top-down view on a display screen of the navigation device. While such an approach provides the navigator with situational awareness, it does not provide the navigator with a true visual perspective, similar to what the navigator would see looking from the navigator's position in the vessel being navigated.
Accordingly, the need exists for an electronic navigational device which provides intuitive presentations of navigation information which are direct and simple to interpret. Particularly, the need exists for a navigational device which displays a presentation of a navigational route in a visual perspective view which is at least substantially true to the relationship of actual positions on or near earth. Specifically, the need exists for an electronic navigational device which displays navigation data in a virtual reality format, wherein the navigation data displayed on the display is presented from a selected perspective location. More specifically, the need exists for a navigation device which displays, on a display screen, a navigation route and way point information similar to a real world perspective view from the navigator's actual location, even where the navigational information displayed includes multiple legs of a route positioned at various angles with respect to each other. The present invention fills these and other needs, including the need to reduce the mental interpretation required by a navigator when viewing a navigation device, while overcoming the drawbacks of the prior art, with a simple solution and implementation of that solution in the device an method disclosed herein.